fix(worker): YouTube importer prefers H.264 so originals import in Premiere

YouTube now packs AV1 inside .mp4, so the old `bv*[ext=mp4]` format selector
grabbed AV1 for the downloaded ORIGINAL. Premiere rejects AV1 on hi-res import
("unsupported file type"). The h264 proxy was fine, but the original wasn't.

Prefer avc1 (H.264) so the original is Premiere-native, falling back to the
previous any-mp4 behaviour only when no H.264 rendition exists. avc1 tops out
at 1080p on YouTube (above that is AV1/VP9 only), which is the universally
importable ceiling anyway.

Verified on a real URL: old selector -> av01 1080p; new selector -> avc1 1080p
(same resolution, now Premiere-native).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/worker/src/workers/youtube-import.js

@@ -67,7 +67,12 @@ async function runYtDlp({ url, outputTemplate, onProgress }) {
       '--no-playlist',
       '--no-warnings',
       '--restrict-filenames',
-      '-f', "bv*[ext=mp4]+ba[ext=m4a]/b[ext=mp4]/b",
+      // Prefer H.264 (avc1) so the downloaded ORIGINAL is Premiere-native.
+      // YouTube now packs AV1 inside .mp4, so the old `bv*[ext=mp4]` selector
+      // grabbed AV1 — which Premiere rejects on hi-res import ("unsupported
+      // file type"). avc1 tops out at 1080p on YouTube; only if no H.264
+      // rendition exists do we fall back to the previous any-mp4 behaviour.
+      '-f', "bv*[vcodec^=avc1]+ba[ext=m4a]/bv*[vcodec^=avc1]+ba/b[vcodec^=avc1]/bv*[ext=mp4]+ba[ext=m4a]/b[ext=mp4]/b",
       '--merge-output-format', 'mp4',
       '--print-json',
       '--newline',